1. Field of the Invention
This invention pertains to a method and a device for the continuous measurement of portal blood pressure. The method and device use an inflatable tamponade balloon inserted into the esophagus and a sensor to monitor the portal blood pressure.
2. The Prior Art
U.S. Pat. No. 5,653,240 to Zimmon, the disclosure of which is herein incorporated by reference, discloses a method and device for measuring portal blood pressure. That invention provides a device and a technically simple method for measuring portal venous pressure in patients with esophageal varices and or portal systemic collateral veins during upper gastrointestinal endoscopy or without endoscopy by positioning the tamponade and sensor with an instrument passed from the mouth into the stomach to provide a rail for introduction and removal. These instruments include an oral-gastric tube, balloon introducer, wire guided dilator, bougie or other similar device. The oral-gastric tube method allows the measurement of portal pressure after tamponade for bleeding without the need for expensive and technically demanding gastrointestinal endoscopy. Such measurements are essential to evaluate the patient's response to drug therapy and determine the therapeutic action required for prevention of recurrent bleeding. An advantage of the above mentioned invention is that in the non-bleeding patient, it allows endoscopic surveillance of esophageal varices combined with measurement of portal venous pressure as a single procedure using only conscious sedation.
However, the use of a large endoscope such as used in the patent mentioned above to observe the collapse of esophageal varices is cumbersome and difficult for the patient, since it requires sedation. It would be desirable to find a method for measuring portal blood pressure that eliminates the need for endoscopy and makes the use of tamponade with sensors available to those without endoscopic skills.
Furthermore there have been numerous endoscopic attempts to measure portal pressure or pressure in esophageal varices. These methods are cumbersome and fail because of the difficulty of identifying the collapse of esophageal varices. The problem is increased when the varices are small. The visual endoscopic methods are limited to operators with considerable endoscopic skill and accept the disabilities of esophageal peristalsis and the need to inflate the esophagus with air that both provokes peristalsis and raises intra-esophageal pressure to limit the accuracy of measurement. This is in contrast to the tamponade method that provides a deflated stomach for continuous esophageal decompression through an esophagogastric sphincter that is breached by the tamponade lumen. Methods requiring needle puncture of varices accept the risk or hemorrhage and are of necessity performed only when endoscopic injection sclerosis of varices in indicated and necessary. Otherwise the risk of bleeding from varix puncture or late bleeding from ulceration associated with varix sclerosis would not be acceptable. All of these esophageal methods measure pressure during continuous flow of blood in the varices in a resistance loop between the portal circulation and a central outflow site that is a derivative pressure. Since the precise site of measurement and its position in the resistance loop is not known, the relationship of the measured pressure to intra-abdominal portal pressure cannot be known and the measurement cannot be reproducible.